It has previously been proposed--see German Pat. No. 22 41 127--to provide apparatus to thread web-like material in rotary printing machines in which different threading paths can be selected. The different threading paths are determined by guide elements and switches located outside of the region of the the rollers or cylinders of the printing machine. A flexible threading element of elongated shape is guided along the guide path in accordance with the predetermined threading path of the web. The guide element can be moved longitudinally to-and-fro. The threading element generally used is a flat spring-like element which can bend in two directions from its major plane; slight additional bending transverse to the plane is possible by twisting the element.
In various machines it is difficult to position the threading element such that it is located in essentially a single plane extending transversely to the major plane of the threading spring which, usually, is made of spring metal.